1. Field of the Invention
The present invention relates to a stabilizer block used in the manufacture of laminated objects. More particularly, the present invention relates to a device used to stabilize the position of layers in a laminate structure when being compressed between the platens of a lamination press.
2. Description of the Related Art
A printed circuit board is an insulated board or panel upon which a plurality of interconnected electronic circuits are mounted. The manufacturing of both single layer and multi-layer circuit boards typically involves using a press to laminate together a plurality of thin layers of material, such as prepreg, copper and/or inner-layer circuit boards, between a pair of metallic plates. Typically, the plurality of layers are stacked atop each other and placed between a pair of protective plates or cauls to form a "lamination book". The lamination book is placed on a carrier tray which is positioned between the platens of a lamination press. The platens are then heated and moved toward one another to compress the lamination book therebetween at a high pressure, such as 100-800 psi.
Unfortunately, the are several difficulties associated with the process of compressing the lamination book within the lamination press. One such difficulty is that the layers in the book tend to move or shift as the platens apply pressure. As heat and pressure are applied, the prepreg melts and becomes less viscous, which often causes the layers to slide relative to one other. Such sliding may undesirably interfere with the correct alignment of the layers of the lamination book relative to the other layers. Additionally, abnormalities in the surfaces of the layers sometimes cause the pressure to be applied unevenly across the surface of the layers. This uneven pressure distribution may build and cause one or more of the layers to dangerously shoot out of the press as pressure is being applied.
In order to avoid such mishaps, the pressure and heat is often increased at a slow and gradual rate to thereby reduce the likelihood of the layers laterally shifting from their desired locations. The slow increase in pressure allows the layers to settle gradually and thus avoid shifting or movement. Unfortunately, a gradual increase in heat and pressure lowers the efficiency of the manufacturing process by increasing the amount of time required to manufacture the laminate structure.
To overcome this problem, some circuit board manufacturers use stabilizer blocks to prevent the layers in the lamination book from shifting during the pressing process. The stabilizer blocks typically comprise a set of blocks having abutment surfaces on one side. The stabilizer blocks are typically positioned on the carrier tray with the abutment surfaces of the blocks positioned around the perimeter of the lamination book to prevent the layers in the book from moving. The blocks are typically mounted with the abutment surface positioned adjacent an edge of the book on pins that are fixedly attached to a set of pin holes in the carrier tray. The coupling of the stabilizer blocks to the pins prevents the stabilizer blocks from moving relative to the carrier tray. However, the pins must be precisely positioned on the carrier tray or else the book may not fit correctly between the blocks once the blocks are mounted to the pins. Moreover, the book must also be precisely positioned relative to the stabilizer blocks. The requirement for such precise positioning of the book reduces manufacturing efficiency. Further, new pin holes may have to be drilled to accommodate different sized books.
Another disadvantage of current stabilizer blocks is that the abutment surfaces of the blocks are generally not configured to compress within the press. The abutment surfaces thus generally have a height that is less than the height of the lamination book so that the stabilizer block will not absorb forces from the platens as they are compressing the book. Because the abutment surface is shorter than the height of the lamination book, there is a likelihood that the uppermost layer in the lamination book might move laterally over the top of the stabilizer block as the book is being compressed.
There is therefore a need for an improved stabilizer block that secures the position of a lamination book during pressing. The stabilizer block should be configured to fit within a press and not interfere with the application of pressure onto the lamination book. Additionally, the stabilizer block should be capable of being easily and quickly positioned on a carrier tray around the perimeter of the lamination book and readily adjustable to accommodate different-sized books.